Study On The Crack Propagation Effect Of Concealed Ground Fissure Under The Influence Of Surface Water Infiltration

Ground fissure is develops in the shallow crust of soil layer of a formation disconnected or cracking phenomenon,by inside and outside the geological forces and human activity is a common cause,and with different structural forms of exposed at surface,for through the ground fissure on the ground or underground structure has great damage,in our country Fen areas,especially in xi 'an,ground fissure development,the worst of urban planning and underground space development has caused great difficulties.Surface water infiltration is an important factor to induce the development of buried ground fractures.On the basis of field investigation,this paper studies the fracture propagation process of ground fractures during surface water infiltration by means of large-scale physical model test and FLAC3 D numerical simulation.The main results of this paper are as follows:(1)data collection under surface water infiltration characteristics of ground fractures in the fenwei basin was conducted,including control factors,profile morphology,development range,distribution characteristics and other factors.Through the collection and analysis of existing data,it is concluded that the restart activities of concealed fractures under surface water infiltration can be divided into four main processes:(1)fault activities;(2)surface water infiltration;(3)hydraulic erosion;(4)shrinkage due to water loss.(2)research on the expansion and development characteristics of positive fault-type buried ground fissures under the action of surface water infiltration was carried out.Nearly erect crack plate under development,on the tilting disc development and not through to the surface of concealed cracks model as an example for large size model test,model test: 1)the lower soil in addition to the vertical crack development no other burst,water table without infiltration channel,thereby footwall development only in the shallow surface of soil infiltration zone;2)the soil mass between vertical fractures and antidip fractures is the main infiltration zone of surface water infiltration,and it is divided into upper and lower parts of soil mass to develop infiltration zone respectively,the upper part to develop infiltration zone from top to bottom,and the deep part to develop reverse development from deep stagnant water from bottom to top.3)surface water infiltration causes the soil body weight stress between fracture zones to rise and shear strength to decline,and finally causes the soil body at the arch bottom of the "earth bridge" to shear slip,and finally the vertical crack and preset crack form an integrated fracture zone.(3)based on the model test,FLAC3 D numerical simulation study of 1:10 was carried out,and the results showed that: 1)the infiltration zone of surface water infiltration basically occurred in the soil body between vertical crack and anti-dip crack;2)the main deformation of soil in the infiltration zone is settlement,and the horizontal tensile deformation is much smaller than settlement.3)the pore pressure of soil body at the "earth bridge" site rises rapidly when the anti-dip crack penetrates to the surface.Meanwhile,the uneven settlement here is more obvious than that of soil body before the anti-dip crack reaches the surface,and the time of shear slip is faster.